The present invention is an improvement over U.S. Pat. No. 5,078,167 issued on Jan. 7, 1992 and entitled FUEL FILTER AND PRESSURE REGULATOR SYSTEM APPARATUS.
In most vehicles having a fuel injection system, such as that shown in U.S. Pat. No. 4,633,901 to Brandt, et al., one fuel line leads from a fuel pump in the tank, through a fuel filter to the engine fuel rail and ultimately to the fuel injectors. The amount of fuel is controlled by a pressure regulator disposed adjacent to the fuel rail and consequently, is located a relatively long distance from the fuel tank. This requires a fuel return line to return unused fuel to the fuel tank.
One of the problems with aforementioned prior art is that there is additional expense in having a fuel rein line and furthermore if this line is broken for any reason, such as in an accident, the fuel could create a fire hazard.
For this reason and others, returnless fuel filter and regulator systems have been proposed, for example, by having the pressure regulator located in the inlet line from the fuel tank, but located adjacent to or attached to the fuel tank. In such a system, then all of the fuel would first pass through a fuel filter before reaching the pressure regulator valve, and if more fuel reaches the regulator valve than needs to be delivered to the fuel rail, then the regulator valve will merely drop the excess fuel back into the tank directly.
Still another returnless system proposed uses a pressure transducer at the fuel rail connected to an engine control computer which controls a variable voltage drive for the fuel pump located in the fuel tank. A fuel filter is of course, used in the fuel line leading from the fuel pump to the fuel rail at the engine injectors. One of the major problems with this type of system is that it is expensive, for example, especially the pressure transducer, variable voltage drive and the type of fuel pump required for use with this system. Furthermore, if the vehicle is accelerating rapidly such that the drive is moving fast, the inertia of the fuel pump could produce excess fuel if the vehicle needs to stop immediately, and this could cause flooding of the engine.
In the first two systems referred to above, since all of the fuel which goes to the regulator must be filtered, a larger filter is required than if only the fuel which actually goes to the fuel rail is filtered. In other words, the return line which dumps fuel back into the fuel tank is dumping clean, filtered fuel back into a tank of unfiltered fuel. This will cause more deposits on the filter than would otherwise be necessary and that is the reason why a larger filter is needed than would be needed for the present invention. It is, of course, well known that as filter becomes clogged with impurities, it will create an increasingly greater pressure drop across the filter. If this pressure drop becomes too great, the required pressure delivered to the fuel rail will be insufficient and the fuel injection system will not operate properly.
The foregoing problems have been previously addressed in U.S. Pat. No. 5,078,167 wherein a valve in fluid communication with the fuel inlet supply tube is provided with a regulator positioned downstream oft he fuel filter for causing the fuel flow to be short circuited back into the fuel supply tank when the pressure in the fuel outlet exceeds a predetermined level. The valve is biased to a closed position and will remain closed when the pressure on the clean side of the filter is below the predetermined pressure, whereby all of the fuel in the fuel inlet supply tube will pass through the filter when the pressure in the fuel outlet is below the predetermined pressure.
While this patented device offers significant advances over the prior art, it is desirable to have a regulator/filter of this type which is responsive to reference pressures other than just the fuel tank pressure as compared to the filter outlet pressure.
Accordingly, there is a need for an improved fuel regulator system which will overcome the aforementioned problems with the prior art.